A calorimeter is commonly used for providing measurements on thermal characteristics of samples. One such calorimeter is a differential scanning calorimeter (DSC) for making measurements on a pair of samples such that a test sample is compared to another test sample or a reference sample, for example, as described in U.S. Pat. No. 3,263,484 (Watson et al). The samples are supported in an insulated container. A power supply provides power to each of the samples and temperatures are measured. In a DSC, differential power and temperature between samples are determined for comparison of heating characteristics such as phase changes. A furnace or other heating vessel is placed over the sample region for heating to provide a range of temperatures for the measurements. Liquid nitrogen or the like in a reservoir below the sample support may be used to extend the DSC to a lower temperature range.
After a test run with a calorimeter to an elevated temperature, but before making another test run, it usually is necessary to cool the sample region back to a starting level which may be room temperature or liquid nitrogen temperature. Typically a cooling chamber surrounds the furnace, for cooling gas to be passed through the region between the chamber walls and the furnace. Such an arrangement is relatively slow to cool the furnace walls and the sample region within, because the air flowing over the walls is warmed and is thereafter inefficient in cooling other wall regions. Such a method generally takes at least 30 minutes to cool from 500.degree. C. to room temperature. Furthermore, because of the non-uniform temperature of the resultant cooling air, the furnace walls vary in temperature, significantly affecting the performance of the calorimeter which then requires some corrective calculations to overcome the physical handicap.
High velocity jets have been used for cooling of surfaces, as disclosed in a paper "Heat Transfer by a Square Array of Round Air Jets Impinging perpendicular to a Flat Surface Including the Effect of Spent Air" by D. M. Kercher and W. Tabakoff, Gas Turbine Conference and Products Show, Cleveland Ohio, Paper No. 69-GT-4 (Mar. 9-13, 1969).